This invention pertains to acoustic devices of the nature of stethoscopes.
The art is replete with ear tips for stethoscopes; from the simple rounded metal ends of the early doctor's scope to later versions for listening to music or the sounds of motion pictures on airplanes.
For the brief use typical of the doctor, comfort to the wearer is not particularly significant, nor is high attenuation of ambient noise, since the ambient sound level is usually low in a hospital room or a doctor's office.
For use for several hours, as by passengers in an airplane, the prior art has usually supplied a mushroom-shaped semi-stiff cushion having an aperture for resting upon the human ear. The wanted sounds come through the aperture, while the cushion tends to exclude ambient sounds.
Other embodiments have had the shape of an expanding horn, with the large diameter thereof pressing upon the ear. The horn may be made hollow between the inner passage that conducts the wanted sound and the outer surface that assists in reducing ambient noise. This makes the embodiment flexible and so to adapt to the general area of the concha of one's ear with minimum pressure applied by the appliance to the ear.
Still another embodiment is merely a relatively large spongesoft cylinder that remains out of the ear, but deformably rests against it.
Currently available earplugs are generally fabricated from plastics containing plasticizers to promote required flexibility. However, the initial flexibility (a relatively high durometer reading) tends to be too high for comfort. The plasticizer uncontrollably leaches out with time, making the ear plug stiffer and more uncomfortable as time goes on.